Controlling apparatus for piston pumps



F. MARTIN. CONTROLLING A ARATus FOR PISTON PUMPS. APPLICATION FILED061123, 1920.

2 SHEETS-SHEET I.

S P M U P N 0 CONTROLLING APPARATUS 2- APPLICATI ON FILED 23, 1920.

Rammed J1me 1922;

-2 SHEETSSHEET 2.

use are FRIEDRICH MARTIN, OF ESSEN GERMAN Y, ASSIGNORLTO FRIED. KRUP]?FATNT] F-FHQL- AKTIE GEsEL mSonAFT, or nss u on-rns-enne, GERMANY,

v miss-a.

CONTROLLING APPARATUS FOR PISTON PUMPS.

Specification of Letters Patent. Patented June 6, 1922.

.e nca'uoninea October as, 1920. Serial No. 419,043.

To all whom'it may concern Be it known that I, F RIEDRIoH MAR'r iv,residing at Essen, Germany, a citizen of the German Republic, haveinvented a certain new and useful Improvement in Controlling Apparatusfor Piston 'Pumps, of which the followingis a specification. Thepresentinvention relates to controlling apparatus for pistonpumps drivenby a shaft and having variable stroke-length, in

which a controlling piston, intendedto alter.

the stroke-length of the working'piston during the operation of thepump, is under the influence of the fluid pressuregenerated by the pumpas Well as of that of a power source acting in opposition to saidpressure, so that the fluid pressure tends to displace the controllingpiston in the direction of diminishing the stroke-length of the workingpiston. If

with a pump of this kind the pressure conduit is shut off duringoperation, an increase of pressure will occur-in the pump, whichcausesashortening of the stroke-length of the piston. If the chambercontaining the shut off pressure fluid were completely tight,

then the stroke-length of the Working piston would bediminished to thevalue of zero,

and a condition of inertia would occur, in which the pump would have nopressure,

evenby continued rotation of the driving shaft. Really, such a conditioncan never be attained with the known pumps. On the contrary, as thestroke-length of the working piston, on account of the. unavoidableleakage, can only be diminished onto an.

amount with which the pump delivers just i so much fluid as correspondsto the losses by leakage, then a condition of inertia will occur withthe saiddiminished stroke-length,

wherein the pump continues to work under high pressure without producinguseful work. In this resides a considerable disad vantage, as the pumpis stressed and worn outunnecessarily.

The present invention has for its object to overcome this disadvantage.

. The invention is illustrated on the accom-- panying drawing as appliedto a m'ultiplecylinder piston pump of a hydraulic power plant,-the axesof the pump cylinders being arranged on a cylindrical surfacearound-adriving shaft common for all the pump cylinders.

-Fig. 1 shows aside elevation, partly in section,of one embodiment ofthe invention,

ing' plant,

0 mounted on the valvebox C.

together with the adjacent parts of the pump- Fig. 2 a section, in lrger scale, ofa modified detail of the subi ect matter of the invention,and Fig. 3 is a view on a larger scale showing the means for varying thestroke-length of the pump.

A is the housing of the pump, to which are connected the suctionspipe-aand a pipe a ofthe pressure system. The pump comprises, as usual,aplur-ality of stationary cylinders A", arranged parallel to theirdriving shaft B, Fig. 3. In each cylinder is a piston L, connected by arod U with a cam disc V, whichis in turnconnected with the housing A bya joint comprising two pairsofpins o and S, at right angles to eachother. The axes of said 'pins intersect in a point 0, forming thecenter-of said joint and lyingin the axis of the shaft B. The cam disc Vis mounted, through a ball bearing W, on a support B, which is adjustably mounted on a disc B rigidly connected with the shaft so that itcan turn, relatively to the latter, about an axis'which lies at rightangles to the axis of shaft B,

at the point 0, To adjust the support B, a

sleeve D is provided, which can slide but not turn upon shaft B, whichis driven. at a constant speed, as by an, electric motor. Sleeve D isprovided, on each side 'of shaft B, with a rack d meshing with a gearsector Z. Each of .these sectors is rotatably mounted on a bridge 6rigid with the disc B and meshes with a gear segment Z2 on the supportB, so that the latter can be turned about its axis, passing throughcenter 0,'by a displacement of sleeve -D, which, accordingly varies thestroke of the piston'L, it being shortened when said sleeve is moved inthe direction of arrow Into the pressure conduit there is insertedbetween-the pipe. of and-a pipe of connected thereto, return valve a thevalve bodya of which, acted upon by a springe tends to shut off the pipea from the pipe (11?, which leads directly to the pump housing- A. Thepipe (1 opens into a central port 0 of a slide 'valve box C, withinwhich a slide valve C may be displaced b'ya hand lever Two ports 0 and care provided in the valve box C,

one on each side of the :central port 0 and adapted to be closedsimultaneously by the slide valve C From the port 0 a pressure the muttD. The other arm of the bell crank lever it has hinged connection,through a link with a single-arm lever F, also rotatablymounteil on thepump housing A. By means oi a rod the lever F is also in ningedconnection with the rod (3: ot a small piston rlisplaceable within acylin der ii said piston rod il having stopcollars g and g As it will beseen from the above given description the piston rod G is in constantpositive connection with the muff D, in such a manner that adisplacement of this piston rod in the direction of the arrow ;1 causesa displacement of the mutt D in the direction of the arrow a2, and, as aconsequence, a shortening of the stroke-length of the working piston Thecollar g is now so arranged that it limits the displaccmentot the pistonrod in the direction of the arrowg/ when the mutt D has arrived in theposition that corresponds to thezero length of the stroke of the workingpiston. On the other hand, the collar 91* limits the displacemcnt'ot thepiston rod. G in the direction opposite to the arrow 3/ when the Inuit Dhas reached the position corresponding to the maximum strokcdength ofthe working piston. The

piston rod G has different diameters on.

both sides of the piston Gr, so that the piston G acts as a differentialpiston, its annular area to the right on the drawingbeing the greater.The free end of the lever. F carries a rollerj and pro ects into a slot7L2 running in axial direction, of a piston rod HP provided with a stopcollar h and carrying a piston H Operating in a cylindenA At its endremote from the piston H, the slot k terminates with an abutment hco-operating with the free end of the lever F which carries the roller7'. The righthandend of the cylinder A is, by means of a passage a,permanently connected with the left-hand end of the cylinder A Theright-hand end of the cylinder A is, moreover, connected with the pipe athrough a pipe a The lefthand end of the cylinder A is connected, bymeans of a pipe 2' with a bottle J, which contains compressed air, thepressure of which is approximately equal to the mean operating pressureof the pump. The right-hand end of the cylinder HQ, and, as aconsequence, also the left-hand end of the cylinder A, are thereforeconstantly under pressure.

ln hearings on the cylinder it is carried bell crank lever hi hi}, theone arm, hi, of which extends into the path of the collar 71, ct thepiston rodlll The other arm, it, of the bell crank lever is connected bymeans oi a link Ill. with a d'oublcnrmcil lever l mounted on the valvecasing N. The link iii extends beyond the lever i and passes through aneyelet 11, on the valve casing it, with suilicient play, so that thebell crank lever iii K and the lever P may rock on restricted withincertain limits.

A rod 2 slidable in the valve casing N, engages one of the arms of thelever P, and another rod p also slidable in the valve casing N, engagesthe other arm of this lever. In the valve casing N are provided twodouble chambers, which each consist of two communicating chambers .21 nand a n. The chamber or? may be shut off from the chamber a, into whichthe rod 11 extends, by means of a valve Q, actuated by a spring whilethe chamber 71* may be shut off from the chamber n, into which the rod20 extends, by .means of a valve R, actuated by a spring 7. Thedescribed parts are so arranged that the two rods 19 and intended foropening these valves, simultaneously abut against the valves Q and B,when the two latter are in their closing position. As long as the arm Kof the .bell crank lever K K is out of touch with the collar 703 of thepiston rod H the lever P, through the in connected with the right-handend of the.

cylinder A through a pipe n The chamber a is connected with the suctionchamber of the. pump through a pipe a and the chamber 1r with therighthand end of the cylin dcr .A through a pipe n collar k is out oftouch with thc arm K of the bell crank lever K K and the valve Q, as aconsequence, is kept in its opening position by the spring m as shown inthe drawing, the right-hand room ofthc cylinder A will consequentlycommunicate with the suction chamber of the pump through the path a n aa n There is consequently no pres sure in this room of the cylinder A Asthe left-hand room of the cylinder AJ, as stated hercabove, isconstantly under pressure, the piston rod G tends, therefore, to move inthe opposite direction to the arrow and keeps, consequently, the roller7 of the lever F in contact with the abutment surface it? of the slot h?of the piston rod As long as the -H both when it is at rest and during adisplacement in anydirection. As lon 'as position the stroke-length ofthe piston of the pump is depending. The position of the collar k is nowselected in suchwise, that than thatstroke-length with when'the piston Hmoves in the direction ,of the arrow y, the collar comes 1n contact withthe arm K of the bell crank lever K K only when the piston H hasattained a position to which corresponds a comparatively shortstroke-length of the working piston., This stroke-length of the workingpiston must, however, be sufliciently greater than the stroke-length byaid of which the pump would deliver only a quantity of fluid whichcorresponds to the losses by leakage which latter may be ascertained byexperience. On-

the further displacement of the piston H in the direction of the arrowy,a force-closing positive connection will therefore exist between thepiston H and the valve Q (by intermediary of the collar it the bellcrank lever K K the rod M, the lever P, and the rod 2 which connectionresults in that the valve Q, approaches to its seat. The positiveconnection, which existed before the collar it comes to'make contactwith the lever arm K, between the piston Hand the vmufl" D, will thenremain unchanged, so

that no further shortening of the strokelength of the working piston.will occur.-

The conditions are now so" chosen. that the length of the piston strokepresent. at the moment when the valve Q reaches its seat, isstill'greater, for a small convenient amount, Which the pump woulddeliver so much fluid only as is lost by leakage.

For the normal operation of the pump, the parts of the describedapparatus are in the position representedin the drawing. The. pistonvalve C is then adjusted in such a manner that th-e pressure pipe 0leading to the workingmachine is inconnection with the pipes a and aleading from the pump, and the pipe ,0 serving to lead off the waste fwater from the working machine, is connected with the drain pipe 0.Further, the collar h of the piston rod H is out of contactwith the armK of the bell crank -lever K K so that the valve Q is held in its openposition by the spring m and consequently the controlling'piston H is inforce-Closing positive connection with the muff D, on the position ofwhich latterthe stroke-length of the working piston depends.

The puinp then operates just as pumps of known art referred to in thepreamble, as the controlling piston H, on whose position thestroke-length of the working piston depends, is subjected to the fluidpressure, in

' the roller 7 of the lever F such-a manner that. the fluid pressuretends to displace the controlling piston in the direction of shorteningthe stroke-length of the working piston, that is, in the direction ofthe arrow 3 If, now,'the consumption of pressure fluid is slight, thenthe piston H adjusts the pump automatically to a correspondingly shortstroke-length of the working piston ;.and inversely, for a greaterconsumption of pressure fluid, to a correspondingly greaterstroke-length.

The individual advantage of the subject matter of'the present inventionwill fully appear if the delivering action of the pump is broken off, byadjusting, the piston valve C so that the-ports 0* andc are closed. Aninished and the rod p will belowered and the rod 0? raised through theintermediary of the bell crank lever K K the rod M and the double-armedlever P. a

As a consequence, the valve Q, under the action of the-spring. g comesto shut off to take its seat, the valve R is lifted by therod p againstthe action of the spring ,1, so that pressure fluid on the right-handside of the piston G enters into the cylinder A from the cylinder Athrough the pipe 71 the chambers n and n passage a and pipe 127. Now thepiston G comes to act as an independent auxiliary motor. The pressurefluid namely acts n'owon both sides of the piston G after'the' valve Rhas been lifted.

As, however, the right-hand annular area of the pistonG is the greaterone, the latter. will of the arro'w-y,.

be displaced in the direction disengaging the abutment surface h of theslot 78. On this displacement of the piston G, the mufi' D is stillfurther displaced .in the direction of the arrow 01:, and the'stroke-length of the working until it finally becomes zero, when thecollar 9 has co ne to strike against the front face ofthe cylinder A.

As no more fluid circulation can take piston consequentlydiminishedstroke-length of the pump is further dlminlltl rec

A F again comes in contact with the abutmenthas been at y ment ot-the parrow 1 1S upossible.

contrary, now moves gradually towards the right under e action of theair pressure existing on it lett-hand side and in consequence of thelealrage existing in the cylinder the pipes a and a, and at the pistonvalve C 911 thisnlovement towards the right the piston H does not actupon the lever l as the sloth is long enough to prevent such action. Thepiston G remains consequently in its extreme position, which correspondsto the zero length of the piston stroke. The arm K of the bell cranklever K which abuts against the collar h oi the piston rod H follows themovement of the piston l'l so that the valve R is' gradually lowered andthe rod p again approaches the valve Q. At that moment, when the valve Bhas reached its closing po sition, the rod p comes in contact with thevalve Q3. On the further travel of the piston H, the valve Q willberaised, so that the right-hand side ot the cylinder A comes again incommunication with the suction chamber of the pump through the path a nn a a its a consequence, the fluid pressure on the leztthand side of thecylinder A preponderates and the piston G then travels to the rightuntil the roller f of the lever surface 71, 01 the piston rod H As thepump 1s now again adjusted to a-strokelength which delivers a fluidquantity that is considerably greater than the losses from leakage, thenthe piston H again travels to the left and the above-described cycle ofactions is repeated. The piston G namely returns to its extreme positioncorresponding to the zero length ofthe piston stroke and remains againfor a longer time in thisposition whereupon it again temporarily movesto the right and immediately thereupon returns to its extreme position.*Therefore the pump with exception of short interruptions, remainswithout pressure. lVith the present invention the disadvantagespresentin pumps of known art as above described, are, therefore avoided,which consist in that the pump, even when it does-not produce any usefulwork, continues to operate-with only a certain dead stroke-lengthcorresponding to the losses by leakage, under higher stress andcorresponding wear.

' If the working machine is to-be restarted, the ports 0 and 0 have tobe opened through the displacement of the piston valve 0*. As

a consequence, the pressure diminishes in the pipes at and a, as well ason the right hand side of pi 11 ll. which latter. actuated by the airpresurc on its left-hand side, now travels quickly to the right. Thismovement of the piston l car -es the piston to travel to the right, m lthe roller of the lever l again comes into contact with the abutn'icntsur'thrce l1, oi the piston rod l l There now again exists a positivetorceclosing connection between the controlling piston H and the mulll), upon the position of which latter the stroke-length ot' the pumpdepends, soon as the piston it has traveled so far that, the resultingstrokelength corresponds to the iluidconsumption of the working machine,the condition o'l inertia again sets in from which the description ofthe operation started.

lit the piston valve C remains a longer time in the closing position,the piston G, as related above, can travel temporarily so 'lar to theright that the roller f of the lever F again comes into contact with theabut-' mentsuorlaceh ot the piston rod H During this movement of thepiston G there will occur an intermediary position to which correspondsa stroke-length with which the pump just would cover the lossesbyleakage. It now the displacement of the piston G should take place veryslowly, it would occur that the pistons G and H, after several movementsback and forth, would at last adjust themselves, so, that the piston G,on the one hand, will assume the intermediary position above mentioned,and the pump, therefore, only delivers so much fluid as the losses byleakage amounts to; and that, on the other hand, the valves Q and R,whose position is controlled by the piston H, simultaneously assumetheir closing position. The pump would then continuously work with thestroke-length corresponding to the position of the piston Gr under highstress and corresponding great wear. In order to avoid thisdisadvantage, which has to be prevented just by thisin'vention, caremust be taken that the piston G is quickly moved .so far out oft-hisextreme position, which corresponds to the zero stroke-length, that the;roller f ,comesinto contact with the abutmentsurface h of the piston rodH For this purpose, with the embodiment represented in Fig. 1, the outerdiameter ofthe valve Q must be large enough so that the passage areapermits a quick flow of the fluid present on the right-hand side of thepiston G in the cylinder A even with very small stroke-length of thevalve Q. In Fig. 2 is shown an embodiment which insures an absolute safemanner of operation, even with comparatively small diameter of the valveQ.

In this second embodiment, a two-part muff T is inserted between the rod37 and I the valve Q, which mufi is slidable upon the rod 79 and bolt ghaving a head and secured to the valve Q. The muff T. has,

on the one hand, an abutment surface 23 with which it is able to makecontact with the head of-the bolt g when it' approaches the valve Q, andon the other hand,--an abut- I ,ment surface 6 for the rod 2 These parts25 Will first be' compressed by the rod p areso arranged that, on theone hand, the rod p 'is in contact with the abutment surface t and, onthe other hand, the abutment- Sui-facet is in contact with the heady; ofthe bolt 9", when the valve Q assumes its closing position and when thelever P is. in that angular position in which in the embodiment of Fig.1 the rod 12 comes to touch the valve Q. Between the muff T and thevalve Q there is inserted a spring 7 t the strength of which is suchthat-when simultaneously the abutment surface t is in contact with thehead 9 of the bolt 9 and the rod 79 with the abutment surface 25 thisspring exerts a force against the-valve Q that is nearly the same as theresistance with which the valve Q actsagainst displacement from: itsclosing to its opening position under the action of the fluid pressureacting upon it and of the pressure of. the spring 9 If now, with thelast described apparatus, a slow displacement of thepiston to the righttakes place after the Zero strokelengthhas been adjusted, then thespring after it has come to touch the abutment surface of the muff T,the valve Q, which is under the influence of the spring 9 and the.fluidpressure, remaining inzits closing position. As soon as, however,on the further movement of the rod 79?, wherein the muff T now partakes,the abutment surface t has come into {contact with the head 9 of thebolt Q2, then'the valve Q is lifted on the further displacement of thepiston 'H,

- 25 over the pressure from the spring 9 and.

the pressure fluid. The valve Q then immediately moves so far in theopening direction, independent of the rod 39 that even with acomparatively small diameter of the valve Q, a passage of suflicientarea'is produced. The pressure fluid can now flow out quickly from thecylinder A, and the Y piston G, as soon as it has started, travelstherefore immediately and without fail so far to the right, that theroller f of the lever Flcomes incontact with the abutment surface h ofthe piston rod H a As the pump from now on is adjusted to astroke-length by which the delivered fluid.

quantity is considerably greater than the losses by leakage, thecontrolling piston H again travels to the left, so that the rod p largerarea of the differential piston G, so

that this latter travels to the left and adjusts the pump'again to thezero stroke-length.

A similar device as is providedto obtain a quick opening movement forthe valve Q, as illustrated in Fig. 2, may naturally also be applied toobtain a merit for the valve R.

I claim? quick opening move- 1. A controlling apparatus for pistonpumpsv with shaft drive and a variable stroke-length comprising anadjusting mem- -'ber for varying the stroke-length of the pump, acontrolling'piston, means connecting said controllingpiston to saidadjusting member, means enabling said controlling piston to be actuatedby the fluid pressure generatedby the pump in the senseof shortening thestroke-length of the pump, a source v oflp'ow'efr acting on thecontrolling piston in opposition to thefluidpressure of the pump, meansfor ad usting the pumpso that it will be without pressure, an auxiliarymotor for actuating said-adjusting means, and means operable by thecontrolling piston when having reached a position corresponding to apump in the sense of shortening the strokeated by the fluid pressuregenerated by the length of the pump, a source of power acting on thecontrolling piston 1n op osition to the fluid pressure of the pump, anmeans operable by the controlling piston when havmg reached a positioncorresponding to a' comparatively "small stroke-length for causing saidauxiliary motor-to function wherediminished to the value-of zero.

by the stroke-length of the pump may be 3.!& controlling apparatus forpiston pumps with shaft drive and a variable stroke-length comprising anadjusting member for varying the stroke-length, a controlling piston andan auxiliary motor, means connecting said controlling piston andauxiliary motor to said adjusting member and allowing the adjustingmem/ber to .be' displaced by said auxiliary motor independently 'of lac100 comparatively small stroke-length forcaussaid controlling piston inthe sense of shortening the stroke-length of the pump. means enablingsaid controlling piston to be actuatedby the fluid pressure generated bythe pump in the sense of shortening the stroke length of the pump, asource of power acting on the controlling piston in oppositionto thefluid pressureof thepump, and means operable by the controlling pistonwhen having reached a position corresponding to a comparatively smallstroke-length for causing said auxiliary motor to function whereby thestroke-length of the pump may be di-. minished to' the value of zero.

4. A controlling apparatus for piston pumps with shaft drive and avar1able stroke-length comprising an adjusting memher for varyingthestroke-length of the pump, a controlling piston, means connecting saidcontrolling piston to said ad ust1ng member, means enabling saidcontrolling piston to be actuated by the fluid pressure generated by thepump in the sense of shortening the stroke-length of the pump, a sourceof power actin on the controlling piston 1n opposition to t e fluidpressure of the pump, means for adjusting the pump so that it Wlll bewithout pressure,an auxiliary motor for actuating said adjusting means,said auxiliary motor having a cylinder, a'piston work ing therein underthe action of the flu1d pressure generated by the pump and a startinggear operable by the controlling piston when having reached a positioncorresponding to a comparatively small-stroke-length for causing saidauxiliary motor to function. I

5. A controlling apparatus for plston pumps with vshaft drive and avariable stroke-length comprising an adjustlng member for varying-thestroke-length of the pump, an auxiliary motor having a cylinderpermanently communlcating on-its one side ing gear for controlling saidother side of:

the cylinder to communicate either with the pressure chamberof the pump,or with said discharge conduit, a controlling piston, means connectingsaid controlling piston and said differential piston to said adjustingmember and allowing the adjusting member to be displaced by saiddifferential piston when drivenby the fluid pressurev acting on itslarger area independently of said controlling plston in the sense ofshortening the stroke length of the pump, means en'- abling saidcontrolling piston to be dis- ;placed by the fluid pressure ofthe. pumpalso in the sense of shortening the strokelength of the pump, and asource of power acting on the controlling piston in oppositionto thefluid pressure of the pump, said starting gear of the auxiliary motorbeing operable by the controlling piston when having reached a positioncorresponding to a comparatively small stroke length for causing saidauxiliary motor to function in the sense of shortening the stroke-lengthof the pump whereby the stroke-length of the pump may be diminished tothe value of zero. a r

6. A controlling apparatus for piston pumps with shaft drive and avariable stroke-length comprising an adjusting member for varying thestroke-length ofthe pump, a controlling piston, means connecting saidcontrolling piston to'said adjusting member, means enabling saidcontrolling -piston to be actuated ,by the fluid pressure generated by.thepump in the sense of shortening. the stroke-length of the pump, asource of power acting on the controlling piston in opposition to'thefluid pressure'of the pump, means for adjusting the pump so that itwill be without pressure, an auxiliary motor for actuating saidadjusting means, said auxiliary motor comprising a cylinder, a pistonworking therein, means connecting said cylinder on the working side ofsaid piston to the pressure chamber of the pump, a discharge conduitcommunicating with said cylinder on the working side of the piston'also,a starting valve for controlling the communication between said cylinderand the pressure chamber of' the pump, a

push rod for opening said starting valve operable by the controllingpiston when'having reached a position corresponding to a comparativelysmallstroke-length, an outlet valve for controlling the communicationbetween said cyllnder and the discharge coii duit, a second push rodpositively connected to said first-named one for opening said outletvalve when said starting valve is closed,

an abutment piece interposed between said second push rod and saidoutlet "alve, and a spring interposed between said outlet valve and saidabutment piece whereby during the opemng of vsaid valve said spring willfirst be compressed. t

7. 'A' controlling apparatus for piston pumps with shaft drive andavariable stroke-length comprising an adjusting member forvarying thestrokedength of the pump a controlling piston, means connectmg saidcontrolling piston to said adjusting member, means enabling saidcontrolling shortening the stroke-length of the pump, a source of poweracting on the controlling piston in oppdsition to the fluid pressure ofthe pump, means for adjusting the pump so that it will be withoutpressure, an auxpiston to be actuated by the fluid pressure generated bythe pump in the sense of iliary motor for actuating said adjustingmeans, said auxiliary motor comprising a cylinder, a piston workingtherein, means connecting said cylinder on the working side of saidpiston to the pressure chamber of the pump, a discharge conduitcommunicating with said cylinder on the working side of the piston also,a starting valve for controlling the conimunication between saidcylinder and the pressure chamber of the pump, a push rod for openingsaid starting valve operable by the controlling piston when havingreached a position corresponding to a comparatively small stroke-length,

-an outlet valve for controlling the communication between said cylinderand the discharge conduit, a second push rod positively connected tosaid first-named one for opening said outlet valve when said startingvalve is closed, an abutment piece interposed between said secondpushrod and said outlet valve and having sliding movement relatively to saidpush rod, and a spring interposed between said outlet valve and saidabutment piece whereby during the opening of said valve said spring willfirst be compressed.

The foregoing spec'ification signed at Essen, Germany, this 17th day ofJune, 1920.

FRIEDRICH MARTIN.

In presence of-' HANS Go'rTsMANN, JOHANN DEGKERS.

